A dietitian explains the link between your gut health and your mood

There are trillions of reasons to love your guts… 38 trillion to be exact. That’s the number of bacteria that reside in our digestive system. Imbalances in these bacteria have been linked to obesity, autoimmune disorders, asthma, allergies and diabetes.

There is also emerging evidence highlighting how our brain function is affected by the microscopic microbes within us. Definite links have been found between depression, anxiety and mood disorders, and an out-of-kilter gut microbiota. So, nourishing our guts may go some way to improving both our physical and our mental health.

It is becoming increasingly apparent that diet and lifestyle play crucial roles in maintaining the health of our gut microbes. In fact, the composition of our microbiota is unique, and it constantly changes depending on what we eat, where we live and the people with whom we interact.

Further, there is a direct line of communication between our guts and our central nervous system, commonly referred to as the “gut-brain axis”. The feeling of butterflies in the tummy is related to this connection. So it makes sense that a happy gut may also mean a happy brain.

Gut bacteria: How your microbiome could help you lose weight and beat depression1:04

It seems the old adage of "you are what you eat" is even more applicable today than it ever was. Modern research suggests that there is one substance that can help you sleep better, lose weight, reduce inflammation and even help cure the blues. What is it? Well, the answer may surprise you.

What does the research suggest?

The research is very much in its infancy. However, there appear to be subtle differences in the microbiota of depressed people compared to otherwise healthy individuals. In animal studies, changes to the diversity and number of gut microbes have been associated with anxiety and depression.

Some studies involving faecal transplantation i.e. the transfer of poo from one organism to another (yes, this is a legitimate therapy) showed a change in behaviour in rats after their microbiota were exposed to poo from humans with depressive symptoms.

Stress has long been considered an important factor in the health of our guts. And irritable bowel syndrome (IBS) can be exacerbated by feelings of stress. IBS is a condition associated with symptoms like diarrhoea, cramping, bloating and wind, but the research shows that a large number of IBS sufferers also suffer from depression and anxiety.

Certain bacterial strains (probiotics) may be useful to help mitigate the release of cortisol, a well-known stress hormone. However, to date, this research has only been carried out on mice.

How do we nourish our microbial ecosystems?

Plants in a garden require water and fertiliser in order to grow well. The same applies to our gut microbiota. We need to provide an environment that allows the bacteria to flourish.

Consuming probiotic-rich foods such as yoghurt, kefir, kombucha, kimchi, sauerkraut etc. is only part of the solution. It’s important to feed your gut microbes with fermentable prebiotic fibre. Prebiotic foods include: garlic, onion, leek, barley, cooked and cooled potato and pasta, as well as rye and wheat. By providing your gut microbes with the sustenance they need, you’ll be ensuring that your gut ecosystem has the best possible environment in order to work its magic.

There is still some way to go to before we understand the capabilities of the gut microbiome and how we can support it to positively impact our mood and mental health. In the meantime, the evidence is encouraging. Boosting your mental health might just be a bowl of pasta or a sandwich away… that’s bound to excite and nourish your gut bugs. Not to mention tantalise your tastebuds.

Joel Feren is a Melbourne-based Accredited Practising Dietitian and media spokesperson for the Dietitians Association of Australia. You can follow Joel @the_nutritionguy.